Analysis of Circulating Current Loss for High-Speed Permanent Magnet Motor

High-speed permanent magnet motors, which are characterized by high power density, are used widely in high-speed centrifugal machinery. The magnetic gap is huge in high-speed permanent magnet motors compared with lower speed counterparts. Therefore, the leakage flux in stator slot can dominate the total flux generated by the winding. With the increase of the rated power of high-speed permanent magnet motors, the area that one coil occupies in one slot increases. Because of different positions of strands in one coil, the inductance of each strand differs, sometimes greatly. The impedance unbalance between the strands results in unbalanced distribution of current in strands, which leads to more winding loss and uneven temperature rise in winding. In this paper, following the calculating inductance of each strand, the currents in each strand are derived from loop current equations. The factors affecting the circulating currents are also investigated by a simplified slot topology and winding parameter. Measures to inhibit the circulating current are also proposed to decrease the circulating current loss. Finally, two measurements of ac resistance are introduced.

[1]  G. Long,et al.  Analysis of magnetic field and circulating current for HTS transformer windings , 2005, IEEE Transactions on Applied Superconductivity.

[2]  Tang Renyuan,et al.  Calculation of end region magnetic field and circulation losses for turbo-generators using a coupled field and circuit equations method , 1990 .

[3]  G. Jewell,et al.  Proximity Loss Study In High Speed Flux-Switching Permanent Magnet Machine , 2009, IEEE Transactions on Magnetics.

[4]  Murgatroyd.  Calculation of proximity losses in multistranded conductor bunches , 1989 .

[5]  M. Kazimierczuk,et al.  Comparison of various methods for calculating the AC resistance of inductors , 2002 .

[6]  Xu Yanliang,et al.  A New Structure for Permanent-Magnet-Biased Axial Hybrid Magnetic Bearings , 2009, IEEE Transactions on Magnetics.

[7]  Z.Q. Zhu,et al.  Strand-level proximity losses in PM machines designed for high-speed operation , 2008, 2008 18th International Conference on Electrical Machines.

[8]  Antero Arkkio,et al.  Time-stepping finite-element analysis of eddy currents in the form-wound stator winding of a cage induction motor supplied from a sinusoidal voltage source , 2008 .

[9]  Masaki Sato,et al.  Calculation method for strand current distributions in armature winding of a turbine generator , 2003 .

[10]  Yi Yang,et al.  Study of circulating current distributions for HTS windings , 2011, International Conference on Advanced Power System Automation and Protection.

[11]  Hossein Heydari,et al.  Multicriteria Optimal Winding Scheme in HTS Transformers by Analytical Hierarchy Process , 2011, IEEE Transactions on Applied Superconductivity.

[12]  Z Kolondzovski,et al.  Power Limits of High-Speed Permanent-Magnet Electrical Machines for Compressor Applications , 2011, IEEE Transactions on Energy Conversion.

[13]  Ka Wai Eric Cheng,et al.  Computation of the AC resistance of multistranded conductor inductors with multilayers for high frequency switching converters , 2000 .

[14]  T. M. Jahns,et al.  Scalability investigation of proximity losses in fractional-slot concentrated winding surface PM machines during high-speed operation , 2011, 2011 IEEE Energy Conversion Congress and Exposition.

[15]  Rafal Wrobel,et al.  Contribution of End-Winding Proximity Losses to Temperature Variation in Electromagnetic Devices , 2012, IEEE Transactions on Industrial Electronics.

[16]  M. Fujita,et al.  Circulating Currents in Stator Coils of Large Turbine Generators and Loss Reduction , 2009, IEEE Transactions on Industry Applications.

[17]  A. Szucs,et al.  Consideration of eddy currents in multi-conductor windings using the finite element method and the elimination of inner nodes , 1999 .

[18]  H. Mohseni,et al.  Balancing Current Distribution in Parallel Windings of Furnace Transformers Using the Genetic Algorithm , 2010, IEEE Transactions on Magnetics.

[19]  Daniel M. Saban,et al.  Study of the Copper Losses in a High-Speed Permanent-Magnet Machine With Form-Wound Windings , 2014, IEEE Transactions on Industrial Electronics.

[20]  M.A. Rahman,et al.  Stiffness analysis of a magnetically suspended bearingless motor with permanent magnet passive positioning , 2005, IEEE Transactions on Magnetics.

[21]  R. de Andrade,et al.  Magnetic Bearing Sets for a Flywheel System , 2007, IEEE Transactions on Applied Superconductivity.

[22]  J. Haldemann,et al.  Transpositions in stator bars of large turbogenerators , 2004, IEEE Transactions on Energy Conversion.

[23]  M. Albach,et al.  Optimized Winding Layout for Minimized Proximity Losses in Coils With Rod Cores , 2008, IEEE Transactions on Magnetics.

[24]  A. Demenko,et al.  Hybrid method for analysis of eddy-current loss in electrical machine winding caused by the main flux , 1988 .

[25]  Jussi Lähteenmäki,et al.  Design and voltage supply of high-speed induction machines , 2002 .

[26]  Jiancheng Fang,et al.  Analysis and Design of Passive Magnetic Bearing and Damping System for High-Speed Compressor , 2012, IEEE Transactions on Magnetics.

[27]  V. Babuska,et al.  A review of technology developments in flywheel attitude control and energy transmission systems , 2004, 2004 IEEE Aerospace Conference Proceedings (IEEE Cat. No.04TH8720).

[28]  S. V. Kulkarni,et al.  Circulating-current loss in transformer windings , 1998 .

[29]  N. Bianchi,et al.  Potentials and limits of high speed PM motors , 2004, 38th IAS Annual Meeting on Conference Record of the Industry Applications Conference, 2003..

[30]  Charles R. Sullivan,et al.  An improved calculation of proximity-effect loss in high-frequency windings of round conductors , 2003, IEEE 34th Annual Conference on Power Electronics Specialist, 2003. PESC '03..

[31]  Jonathan Bremner,et al.  Influence of PWM on the Proximity Loss in Permanent-Magnet Brushless AC Machines , 2008, IEEE Transactions on Industry Applications.